The Veterinary Resources Program, National Center for Research Resources, has established a Watanabe hyperlipidemic (WHHL) rabbit breeding colony as a resource for investigators. Watanabe et al reported that there are two types of WHHL rabbits--those with early development and high incidence of coronary atherosclerosis (type 1) and those with late development and low incidence of coronary atherosclerosis (type 2). It has also been shown that either type of rabbit can be selectively bred to produce progeny exhibiting the phenotype of interest. Recently, it was reported that these two types of WHHL rabbits can be differentiated by their lipoprotein phenotypes. Electrophoretic analysis of 14 rabbits from the NIH WHHL rabbit colony showed that there are two lipoprotein phenotypes: one with an increased density of beta-lipoprotein and another with a beta-doublet. These phenotypes are similar to those reported for the two types of WHHL rabbits.